(a) Field of the Invention
The present invention relates to a novel ligand compound, a preparation method thereof, a transition metal compound including the ligand compound, and a preparation method thereof. This application claims the benefit of Korean Patent Application No. 10-2012-0143806, filed in the Korean Intellectual Property Office on Dec. 11, 2012, Korean Patent Application No. 10-2012-0143809, filed in the Korean Intellectual Property Office on Dec. 11, 2012, and Korean Patent Application No. 10-2013-0140006, filed in the Korean Intellectual Property Office on Nov. 18, 2013, which are all hereby incorporated by reference in their entireties into this application.
(b) Description of the Related Art
For a long time, there have been many advances in metallocene catalyst for olefin polymerization. Metallocene compounds are generally activated by an aluminoxane, a borane, a borate, or other activators to be used. For example, a metallocene compound having a ligand including cyclopentadienyl group and two sigma chloride ligands uses an aluminoxane as an activator. It was reported that the activity of the catalyst may increase when the chloride group of such metallocene compound is substituted with other ligands (for example, benzyl group or trimethylsilylmethyl group (—CH2SiMe3)).
European Patent No. 1462464 discloses a polymerization example using a hafnium metallocene compound including chloride, benzyl, and trimethylsilylmethyl groups. In addition, it was reported that the generation energy of activated species may vary according to the alkyl ligand combined to the center metal (J. Am. Chem. Soc. 2000, 122, 10358). Korean Patent No. 820542 discloses a catalyst for olefin polymerization having a quinoline-based ligand, and this patent relates to a catalyst having a leaving group including silicone or germanium atom in addition to methyl group.
Dow Co. had presented [Me2Si(Me4C5)NtBu]TiCl2 (Constrained-Geometry Catalyst, hereinafter ‘CGC’) in the early 1990's (U.S. Pat. No. 5,064,802), the superior aspects of the CGC to prior known metallocene catalysts in copolymerization reaction of ethylene and α-olefin can be largely summarized into two ways as follows: (1) it shows high activity even in high polymerization temperature and forms a polymer of high molecular weight, (2) the copolymerizing ability of α-olefin such as 1-hexene and 1-octene which have large steric hindrance is also very excellent. As various characteristics in the polymerization reaction of the CGC became gradually known, there have been many efforts to synthesize derivatives of the same for using it as a polymerization catalyst in the academic world and the industrial world.
As an approaching method, a synthesis of a metal compound to which various bridges and nitrogen substituents are introduced instead of silicone bridges and a polymerization using the same have been attempted. Representative metal compounds known up to recently include phosphorus, ethylene or propylene, methylidene, and methylene bridges respectively introduced thereto instead of silicone bridge of CGC structure, but they didn't show excellent results in the aspects of polymerization activity or copolymerization performance in comparison to CGC when they were applied to polymerization of ethylene or copolymerization of ethylene and alpha olefins.
As other approaching method, compounds including oxido ligands instead of amido ligands of the CGC have been largely synthesized and polymerizations using the same have been partially attempted.
However, very few catalysts have been being applied in practice in commercial factories among above attempts.